Method of electronic fuel injection feedback control

A method of feedback control for an electronic fuel injection system in an internal combustion engine, said method comprising the steps of:

• reading and filtering a voltage signal from the rear O.sub.2 sensor;
• obtaining a target voltage for the rear O.sub.2 sensor based on RPM and MAP of the engine;
• calculating a front O.sub.2 sensor switching voltage threshold based on a signal from a front O.sub.2 sensor upstream of a catalyst in an exhaust system for the engine and from a rear O.sub.2 sensor downstream of the catalyst;
• comparing a voltage output of the front O.sub.2 sensor to the calculated front O.sub.2 sensor switching voltage threshold to determine if a fuel/air ratio of the engine is rich or lean;
• and
• decreasing or increasing an amount of fuel to the engine by fuel injectors of the electronic fuel injection system if the fuel/air ratio is determined rich or lean, respectively.

A method of feedback control for an electronic fuel injection system in an internal combustion engine, said method comprising the steps of:

• determining whether predetermined conditions have been met for feedback from the rear O.sub.2 sensor;
• reading and filtering a voltage signal from the rear O.sub.2 sensor;
• calculating a front O.sub.2 sensor switching voltage threshold based on a signal from a front O.sub.2 sensor upstream of a catalyst in an exhaust system for the engine and from a rear O.sub.2 sensor downstream of the catalyst;
• comparing a voltage output of the front O.sub.2 sensor to the calculated front O.sub.2 sensor switching voltage threshold to determine if a fuel/air ratio of the engine is rich or lean;
• and
• decreasing or increasing an amount of fuel to the engine by fuel injectors of the electronic fuel injection system if the fuel/air ratio is determined rich or lean, respectively;
• and
• using previously adapted front O.sub.2 sensor switching voltage threshold if predetermined conditions have not been met for feedback from the rear O.sub.2 sensor.

A method of feedback control for an electronic fuel injection system in an internal combustion engine, said method comprising the steps of:

• determining whether predetermined conditions have been met for feedback from the rear O.sub.2 sensor;
• reading and filtering a voltage signal from the rear O.sub.2 sensor;
• calculating a front O.sub.2 sensor switching voltage threshold based on a signal from a front O.sub.2 sensor upstream of a catalyst in an exhaust system for the engine and from a rear O.sub.2 sensor downstream of the catalyst;
• comparing a voltage output of the front O.sub.2 sensor to the calculated front O.sub.2 sensor switching voltage threshold to determine if a fuel/air ratio of the engine is rich or lean;
• and
• decreasing or increasing an amount of fuel to the engine by fuel injectors of the electronic fuel injection system if the fuel/air ratio is determined rich or lean, respectively;
• determining whether predetermined conditions have been met for feedback from the front O.sub.2 sensor;
• and
• using open loop control if the predetermined conditions have not been met for feedback from the front O.sub.2 sensor.

A method of feedback control for an electronic fuel injection system in an internal combustion engine, said method comprising the steps of:

• reading and filtering a voltage signal from a rear O.sub.2 sensor downstream of a catalyst in an exhaust system for the engine and obtaining a target voltage for the rear O.sub.2 sensor based on RPM and MAP of the engine;
• calculating a front O.sub.2 sensor switching voltage threshold based on a signal from a front O.sub.2 sensor upstream of the catalyst and from the voltage signal from the rear O.sub.2 sensor;
• comparing a voltage output of the front O.sub.2 sensor to the calculated front O.sub.2 sensor voltage threshold to determine if a fuel/air ratio of the engine is rich or lean;
• and
• decreasing or increasing an amount of fuel to the engine by fuel injectors of the electronic fuel injection system if the fuel/air ratio is determined rich or lean, respectively.